Engine systems comprise an internal combustion engine equipped with intake manifold and exhaust manifold. Turbochargers are provided for charging air into the intake manifold at increased pressure. Turbochargers generally comprise a turbine which rotates a compressor through a connecting shaft. A typical turbocharged engine system is the so-called single-stage turbocharged system.
A single-stage turbocharged system comprises a single turbocharger arranged for charging air into the engine. The compressor of turbocharger is located in the intake line between the air inlet and the intake manifold, for compressing the airflow and for providing it to the engine. The turbine of turbocharger is located in the exhaust line between the exhaust manifold and the exhaust outlet, for converting the exhaust gas heat to torque which is used to drive the compressor. An air cooler is generally located in the intake line downstream the compressor of turbocharger, for cooling airflow before entering the intake manifold. A drawback of single-stage turbocharged engine systems is the well-known “turbo-lag”.
In order to overcome “turbo-lag”, has been proposed the so-called two-stage turbocharged engine systems, which comprise two sequential turbochargers which are selectively operated in accordance with engine speed and engine load. As a matter of fact, a two-stage turbocharged engine system comprises a high-pressure turbocharger and a low-pressure turbocharger, both having a compressor and a turbine. The compressor of high-pressure turbocharger is located in the intake line downstream the compressor of low-pressure turbocharger, relative to the flow direction.
It follows that the intake line comprises a low-pressure intake line for fluidly connecting the outlet of the low-pressure compressor to the inlet of high-pressure compressor, and a high-pressure intake line for fluidly connecting the outlet of high-pressure compressor to the inlet of the cooler device.
High-pressure turbocharger and low-pressure turbocharger are arranged such that at low engine speeds both turbochargers are used for charging air into the engine, and that as engine speed rises the high-pressure turbocharger is gradually disabled. The intake line comprises a bypass device arranged for allowing the airflow to bypass the high-pressure compressor when the high-pressure turbocharger is disabled. The bypass device generally comprises a bypass line for fluidly connecting low-pressure intake line directly to high-pressure intake line, and a valve which is located in said bypass line for opening or closing the passageway.
A two-stage turbocharged engine system of this kind is disclosed in EP 1 843 019. According to the specific embodiment shown in EP 1 843 019, high-pressure turbocharger and low-pressure turbocharger are aligned and have the respective turbines facing towards each other, so that the respective compressors are substantially located on opposite sides of the engine. In such an embodiment, the bypass device is located close to high-pressure compressor. As a matter of fact, the bypass line is arranged for locally bypassing the high-pressure compressor, and accordingly the valve is located nearby. For cost saving reasons, it would be useful to install the two-stage turbocharged engine system of EP 1 843 019 in the engine compartment of vehicles which are originally designed for receiving a single-stage turbocharged engine system.
However, actual implementation does not comply with the best practice for components arrangement in engine compartment, such that it involves some drawbacks which will be clarified later in the description.
At least one aim of the present invention is to improve the two-stage turbocharged engine system of EP 1 843 019, in order to make possible its installation in an engine compartment designed for a single-stage turbocharged engine system, overcoming the drawbacks of the actual implementation. Another aim of the present invention is to meet the goal with a rather simple, rational and inexpensive solution. In addition, other aims, desirable features, and characteristics will become apparent from the subsequent detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.